1. Field of the Invention
The present invention generally relates to a clutch actuator that disengages and engages a clutch. More particularly, the present invention relates to an engine unit that includes such a clutch actuator and a saddle type vehicle, such as a motorcycle, that includes such an engine unit.
2. Description of the Related Art
Conventionally, a system is known that attaches an actuator to a previously existing manual transmission. The actuator is used to automate certain operations such that the system can automate a series of start, stop and shift change operations (clutch disengagement, gear change, and clutch engagement) based on the rider's intention or the state of the vehicle.
Among the actuators used in the above-described system, one example of a clutch actuator for disengaging and engaging the clutch is the clutch actuator disclosed in JP-A-2005-282784. This clutch actuator is provided with a motor, and a worm shaft that rotates coaxially with a motor shaft of the motor. A tip of the worm shaft is formed with a threaded section. In addition, the clutch actuator includes a worm wheel that meshes with the threaded section; a crank shaft that converts rotational motion of the worm wheel to linear reciprocating motion; and an output rod that is connected to the crank shaft. The clutch actuator finally converts the rotational motion of the motor to an axial reciprocating motion of the output rod, and uses the reciprocating motion of the output rod to disengage and engage the clutch. The clutch actuator also includes an assist spring that is connected to a shaft member of the crank shaft (i.e., a shaft member of the worm wheel).